Turn diameter

[Roelf]

Hi Guys

I have just bought myself the HO 4-8-4 Niagara Steam Loco New York Central #6020 and would like to know which turn radias will suit this loco. My other Steam Locos are 0-6-0 and 2-6-0 Locos. At the moment I sit with 18 and 22 turns?

[SteamGene]

The older Niagras, which is what the NYC called their 4-8-4s, could handle 18 inch radii.  I don't know about the newer ones.  I'm sure it will work on 22" easily.  In any event, the rule of thumb is:  The largest radius you can fit in is what is best.
Gene

[Roelf]

Morning SteamGene

I tested it last night on the 18' and 22' turns. It went ok, but then started to keep on climbing off the track on the one 18' turn. I checked the track and found it uneven at the joint. Fixed it and then it started to do it at another turn. checked the track and the joint was smooth. Even by slowing down it kept on doing the same at the same turn.

[r.cprmier]

Roelf;
Uneven track-by that I mean when the track is laid down, one rail sits higher than the other-wavy sort of.  If this is the villian, then what is happening is that-and on turns, this will really jump out and bite you-the higher side will tend to push the wheels off of the lower side.   This would really be obvious if the engine is slipping over the outer rail.  In a way, it is simple physics, because your mass (loco) wants to keep moving in a tangent that is straight, rather than conform to the curve (the path of least resistance would be the straight line)   It is pretty easy to picture in your mind.  One way to check for this is to take a small level and go across the rails (with power off) and note any differences as you move through the radius.

RIch

[SteamGene]

Rich,
If I'm not mistaken, raising the outer rail by just a bit - say the height of a very thin piece of cardboard or something like 0.10 does the same thing as superelevation - but it MUST be the outside rail, never the inside one.   
Gene

[r.cprmier]

Gene;
That is fine.  What I am referring to is an irregularity in the rail heights-like that of an undulating quality, where you have an inconsistency of one as opposed to the other. 
Second; the outter rail is not as likely to cause this as a higher inside rail, given the same circumstances.  In short, if you have a dip at a portion of the outside rail on a curve, you can bet the engine will be on the ties sooner or later.

Given the quality per se of section al and flex, the likliness of this happening is diminished to a point, but it is still worthy of examination.
RIch